Pyrrolidine (135 μL, 1.62 mmol) was dissolved in anhydrous tetrahydrofuran (1 mL), and 1.6 M hexane solution of n-butyl litium was added dropwise thereto at 0° C. After the reaction mixture was stirred at same temperature for 30 minutes, an anhydrous tetrahydrofuran solution (3 mL) of 2,2,4-trimethyl-1,2-dihydro-6-oxa-1-azachrysen-5-one (Reference Compound No. 1-1, 80 mg, 0.27 mmol) was dropped and then the reaction mixture was stirred for 30 minutes more. After the saturated aqueous NH4Cl solution (5 mL) was added to the reaction mixture, the reaction mixture was diluted with ethyl acetate (100 mL). The whole was washed with water (100 mL) and saturated brine (50 mL) successively, dried over anhydrous magnesium sulfate, and then the solvent was removed under reduced pressure. The obtained residue was purified by silica gel column chromatography (hexane-ethyl acetate) to give the titled compound (80.2 mg) as a pale yellow solid. (Yield 82%)
